1. Field of the Invention
The present invention relates to an aluminum alloy and a slide bearing.
2. Description of the Related Art
In high speed and high contact pressure applications of slide bearings, in particular bearings for internal combustion engines (control rod bearings), the high temperature strength must be raised to secure fatigue strength at high temperatures. Simultaneously, the room temperature strength must be lowered to secure conformability at room temperature. It is impossible however in practice to simultaneously satisfy the required high temperature high strength and room temperature low strength with a single material.
Therefore, in the past, the practice has been to fabricate the bearing body by the good high temperature strength Kelmet (Cu-20 to 45PB) to secure the overall high temperature strength and cover the bearing part with Pb to secure the conformability at room temperature.
On the other hand, the assignee, as disclosed in Japanese Patent Application No. 2001-110347, previously developed an aluminum alloy containing 2 to 20 wt % of Sn, 0.1 to 3 wt % of Cu, 0.1 to 4.5 vol % of TiC having an average particle size of not more than 0.2 xcexcm, and the balance of Al and unavoidable impurities. This alloy secured room temperature low strength (conformability) by the Sn and simultaneously secured high temperature high strength (high temperature fatigue strength) by the Cu and TiC particles and could give extremely superior properties when used for a slide bearing.
The above alloy, however, was limited in the following respects from the viewpoint of the achievement of high temperature high strength:
(1) The scope of application was limited to a very narrow range of models of vehicles etc. It was possible to increase the high temperature strength by increasing the amount of TiC particles, but the room temperature strength simultaneously became higher, so the conformability dropped and seizure ended up occurring. Therefore, a new means enabling the high temperature strength to be raised while keeping down the rise in room temperature strength without increasing the amount of TiC particles is required.
(2) TiC particles are expensive, so a rise in cost is unavoidable. To obtain high temperature high strength, the dispersed reinforcing particles have to be on average not more than 0.2 xcexcm or extremely fine. Production of such fine particles requires in-situ production. (xe2x80x9cin-situ productionxe2x80x9d includes the method based on slow temperature rise and high temperature soaking disclosed by the assignee in Japanese Patent No. 2734891, the method based on rapid temperature rise and self generation of heat disclosed by the assignee in Japanese Unexamined Patent Publication (Kokai) No. 2000-144281, etc.) Even in that case, production of fine particles can be achieved in the above way only for TiC. Therefore, a new means able to be applied to dispersed reinforcing particles other than TiC so as to raise the high temperature strength without requiring the dispersed reinforcing particles to be made finer in the above way is required.
An object of the present invention is to provide an aluminum alloy which is able to use not only expensive TiC particles, but also inexpensive dispersed reinforcing particles and which is further raised in high temperature strength without requiring an increase in the amount of dispersed reinforcing particles and a slide bearing using that alloy.
To attain the above object, according to a first aspect of the present invention, there is provided an aluminum alloy comprised of:
Sn: 2 to 20 wt %,
Cu: 0.1 to 3 wt %,
Ca: 0.02 to 1.5 wt %,
at least one element selected from the group comprised of Mg, Cr, Zr, Mn, V, Ni, and Fe: not more than 2 wt % in total,
at least one type of reinforcing particle selected from the group comprised of TiC particles, ZrC particles, and Al2O3 particles: 0.1 to 5 vol % in total, and
the balance of Al and unavoidable impurities.
According to a second aspect of the present invention, there is provided a slide bearing comprised of the above aluminum alloy of the present invention
The present inventors discovered that by the addition of a suitable amount of Ca in particular, even if using ZrC particles or Al2O3 particles, not just TiC particles, it is possible to increase the strength without increasing the amount of reinforcing particles. That is, according to the present invention, it is possible to raise the high temperature strength without causing a deterioration in the conformability due to the increased amount of reinforcing particles.
According to a third aspect of the present invention, there is provided a slide bearing comprised of a bearing body made of the aluminum alloy of the present invention provided on its surface with a resin coating layer, wherein the resin coating layer contains 70 to 30 vol % of a soft, good high temperature elongation heat-curing resin having properties at 25xc2x0 C. of a tensile strength of 70 to 110 MPa and an elongation of 7 to 20% and properties at 200xc2x0 C. of a tensile strength of at least 15 MPa and an elongation of at least 20% and 30 to 70 vol % of a solid lubricant (here, the total of the two being 100 vol %) and wherein the Vicker""s hardness Hv of the resin coating layer is not more than 20.
The above resin coating layer is disclosed by the present assignee in Japanese Patent Application No. 2000-246354. By bonding the solid lubricant with the soft, good high temperature elongation heat-curing resin, the conformability and heat resistance are secured without peeling as in the past.
By providing this resin coating layer at the surface of the bearing body comprised of the aluminum alloy of the present invention, it is possible to further improve the conformability and possible to expand the scope of application in models of vehicles etc.